我在 SMALLINT 数据类型的数据库security_role_cd列。我使用下面的code到可空INT 变量选择此列。

我收到以下错误：

错误3的条件EX pression类型无法确定，因为没有之间的空与短

什么是正确的code克服这种错误？

  SELECT R.security_role_cd从Security_Role R其中security_role_name ='管理员'
 

C＃

 诠释？ roleID = NULL;
        字符串的CommandText =SELECT R.security_role_cd从Security_Role R其中security_role_name = @rolename;
        SqlCommand的命令=新的SqlCommand（CommandText中，连接）;
        command.CommandType = System.Data.CommandType.Text;
        command.Parameters.AddWithValue（@角色名，角色名）;
        SqlDataReader的readerRole = Command.ExecuteReader却（）;
        如果（readerRole.HasRows）
        {
            而（readerRole.Read（））
            {
                roleID = readerRole.GetInt16（0）== 0？空：readerRole.GetInt16（0）;

            }
        }
        readerRole.Close（）;
 

解决方案

它只是需要知道如何的键入的的空：

  roleID = readerRole.GetInt16（0）== 0？ （INT？）空：（INT）readerRole.GetInt16（0）;
 

我个人倒缓存值，但：

  INT TMP = readerRole.GetInt16（0）; //隐式扩大在这里诠释
roleID = TMP == 0？ （INT？）空：TMP;
 

虽然我也想叫成疑问转动的智慧 0 到空 - 最好使用 IsDBNull以便 - 是这样的：

 如果（reader.IsDBNull（0））{
    roleID = NULL;
} 其他 {
    roleID =（int）的readerRole.GetInt16（0）;
}
 

I have a security_role_cd column in database of smallint datatype. I am selecting this column using following code into a nullable int variable.

I am getting following error:

Error 3 Type of conditional expression cannot be determined because there is no implicit conversion between 'null' and 'short'

What is the correct code to overcome this error?

SELECT R.security_role_cd  FROM Security_Role R WHERE security_role_name = 'Admin'

C#

        int? roleID = null;
        string commandText = "SELECT R.security_role_cd  FROM Security_Role R WHERE security_role_name = @roleName";
        SqlCommand command = new SqlCommand(commandText, connection);
        command.CommandType = System.Data.CommandType.Text;
        command.Parameters.AddWithValue("@roleName",roleName);
        SqlDataReader readerRole = command.ExecuteReader();
        if (readerRole.HasRows)
        {
            while (readerRole.Read())
            {
                roleID = readerRole.GetInt16(0) == 0 ? null : readerRole.GetInt16(0) ;

            }
        }
        readerRole.Close();

It just needs to know how to type the null:

roleID = readerRole.GetInt16(0) == 0 ? (int?)null : (int)readerRole.GetInt16(0);

Personally I'd cache the value though:

int tmp = readerRole.GetInt16(0); // implicit widening to int here
roleID = tmp == 0 ? (int?)null : tmp;

Although I'd also call into doubt the wisdom of turning a 0 into a null - better to use IsDBNull - something like:

if(reader.IsDBNull(0)) {
    roleID = null;
} else {
    roleID = (int)readerRole.GetInt16(0);
}